The present invention relates to sterilization of drinking water and drinking water containers by inactivation of microorganisms located therein and/or thereon. More particularly, the present invention relates to sterilization of drinking water and drinking water bottles using pulsed light sterilization of sealed drinking water bottles. Also described herein, are methods and apparatus for the sterilization of drinking water and drinking water containers by deactivation of microorganisms in drinking water or on said drinking water containers including sterilization of drinking water after being sealed within a drinking water container, using high-intensity, short-duration pulses of incoherent, polychromatic light in a broad spectrum. Finally, the present invention relates to monitoring and controlling key pulsed light parameters to verify sterilization has been achieved.
Various methods of sterilization are known to those of skill in the art, including for example, heat sterilization, e.g., autoclaving, irradiation sterilization, e.g., using gamma radiation, and chemical sterilization. These conventional methods are unsuited to the sterilization of drinking water for a variety of reasons.
A typical drinking water purification process as currently practiced in the art treats water with a series of filters and perhaps other water treatment devices. After filtration and treatment the drinking water is containerized. For example, a water source is provided which introduces drinking water into a multimedia filter which the directs the filtered water into, for example, an activated carbon filter which directs the twice filtered water into a cartridge filter, for example, a 1 xcexcm filter. This thrice filtered drinking water can then be treated with UV radiation or ozone treated before being introduce to a drinking water container which is filled and capped. This allows ample opportunity for post filtration/treatment contamination of the drinking water. Numerous other water treatment schemes have been tried but none have the advantage of being able to treat drinking water after it has been sealed within its container.
A more recently developed, and hence less well known, method of deactivating microorganisms on and/or within target objects uses high-intensity, short-duration pulses of incoherent, polychromatic light in a broad spectrum to sterilize target objects.
The polychromatic light sterilization techniques and apparatus embodied in the present invention has several significant advantages over conventional sterilization techniques. The first being that the present invention accomplishes sterilization far more quickly than conventional methods. The embodiments of the present invention can sterilize most drinking water and most sizes of drinking water containers in less than a few minutes, as only a few flashes, having durations of a few seconds to less than a minute, are required to achieve sterilization. Second, high-intensity, short-duration pulses of incoherent, polychromatic light can achieve a degree of sterility not possible with current drinking water purification techniques. Also, the embodiments of the present invention accomplish this goal with a higher degree of reliability than purification techniques commonly used to purify drinking water. Third, the present embodiments accomplish these goals using less floor space and at less cost.
An example of these advantages is demonstrated by comparison with the current best method of sterilization, autoclaving. Autoclaving requires, a great deal of time to complete (2-3 hours) and has a high energy cost associated with water heating. Moreover, to autoclave the large amounts of water needed in commercial drinking water applications requires huge amounts of floor space to house the autoclaving machines. These cost and space constraints are so prohibitive that autoclaving is not used to purify drinking water. The methods and embodiments of the present invention allow high volume sterilization of drinking water and drinking water containers in a much smaller space than autoclaving while taking far less time.
A further limitation of conventional methods of terminal sterilization, such as autoclaving, is that they are unsuitable for use with polyethylene containers or thin polypropylene containers, because such containers are unable to withstand the temperatures (e.g., between 100 and 200xc2x0 C.) or pressures of autoclaving (polypropylene containers are able to withstand some amount of commercially useful autoclaving, however, they are required to be thicker and more expensive to withstand autoclaving than would need be in the absence of this high heat and pressure treatment). Thus, there exists a need for an approach to deactivating microorganisms in drinking water through a container that does not require the use of heat that may damage the container or its contents.
The embodiments of the present invention can sterilize drinking water contained in many different types of packaging materials, such as olefins (e.g., polyethylene or polypropylene); nylon, or a composite material, either laminated or co-extruded structure (including both monolayer and multilayer structures), and the like. The term container as used herein is intended to be interpreted broadly, including but not limited to, bags, bottles, hoses, tubes, water feed lines, or other means of containing drinking water.
Other sterilization processes, e.g., using gamma radiation to achieve terminal sterilization can damage the polymeric structure of olefin containers (i.e., gamma radiation degrades container integrity), which can result in weakened container integrity, leakage, increased gas permeability and other such problems. Gamma radiation can also attack the container and/or its contents to produce other adverse changes, such as darkening, off-colors or color changes, etc. in the container or its contents. Furthermore, gamma radiation inherently causes the generation of highly reactive species, such as hydroxyl radicals, during the gamma irradiation of water, that may detrimentally alter the chemical structure of the product being treated. Thus, there exists a need for an improved sterilization process usable with polyolefins and the like that does not employ gamma radiation, or other such reactive processes, to achieve sterilization.
Other problems with heat treatment, i.e., autoclaving, and conventional gamma radiation treatment techniques include the xe2x80x9cbatchxe2x80x9d nature of such processes. Specifically, with heat or gamma radiation treatment, product containers are treated in groups or batches, which problematically requires additional handling of the product not required if an on-line continuous process is used. In addition, careful inventorying and product handling are required in order to assure that each batch is segregated, and separately treated and tested.
Using conventional terminal sterilization techniques it is nearly impossible to monitor all of the parameters necessary to assure adequate deactivation of microorganisms in all of the product containers in a given batch (i.e., parametric control is nearly impossible). (For example, it is difficult to monitor the temperature within the autoclave at enough points so than one can assure that every part of every container in the batch received enough heat and saturated steam pressure to achieve adequate deactivation of microorganisms.) Because such parametric control is not generally possible with heretofore employed terminal sterilization techniques, such containers must be observed after treatment, e.g., a fourteen day period following terminal sterilization to determine whether any contaminants are present in selected (or all) containers from each batch. This unfortunately further complicates product and product container treatment and delays usage of the containers and products having been treated. An approach that can be performed in a continuous manner, e.g., as a part of a packaging process, thus eliminating the need for xe2x80x9cbatchxe2x80x9d handling and xe2x80x9cbatchxe2x80x9d testing; and an approach that allows adequate parametric control over processing parameters needed to assure adequate sterility levels, thus eliminating the need for an observation period following treatment, would be highly advantageous.
A generally accepted standard for sterility is, for example, less than one in a million (10xe2x88x926) survivor probability among microbial contaminants. In other words, there must be less than once chance in a million that viable microorganisms are present in a sterilized article. This level of sterilization is referred to as a sterility assurance level of 10xe2x88x926. Until now, this level of sterility has not be achievable in a practical sense in drinking water.
In addition to the difficulties inherent in achieving the requisite sterility in drinking water by conventional methods, is the ability to verify that such sterility levels have been attained. Ordinarily, xe2x80x9csterilizedxe2x80x9d containers must be observed for a period of time, e.g., for fourteen days, following terminal sterilization to determine whether any contaminants are present. This, unfortunately, further complicates drinking water treatment processing and further increases the processing time. An approach that can be performed in a continuous manner, e.g., as a part of a packaging process, can eliminate the need for batch handling and batch testing. Moreover, a sterilization approach that allows adequate parametric control over processing parameters to assure adequate sterility levels can eliminate the need for an observation period following treatment.
Therefore, what is needed is an approach to rapidly deactivating microorganisms inside a sealed drinking water container which achieves an easily verifiable sterility assurance level of at least, for example, 10xe2x88x926, but which approach also reduces damage to the drinking water container.
The present invention advantageously addresses the above and other needs.
The present invention advantageously addresses the needs above as well as other needs by providing an approach for deactivating microorganisms, and more particularly for the deactivating of microorganisms within drinking water containers, and within the drinking water contents of such containers, using high-intensity, short-duration pulses of incoherent, polychromatic light in a broad spectrum directed at the containers, filled and/or empty, so as to penetrate the containers and deactivate microorganisms inside said container, particularly on interior container surfaces and/or suspended in the volume of drinking water contained within the containers.
In one embodiment, the invention can be characterized as an apparatus for sterilizing microorganisms in a container. Such apparatus employs the container, which includes a polyolefin, and which transmits light in a spectrum containing wavelengths selected from between 120 nm and 2600 nm, e.g., wavelengths between 180 nm and 1500 nm or, e.g., between 180 nm and 380 nm. The container may include an input port through which drinking water may be introduced into the container. The port may include threads onto which a threaded cap may be screwed and secured. Typically, the cap is unscrewed or otherwise removed before introduction of drinking water. Such input ports are well known in the art. A flashlamp system generates high-intensity, short-duration pulses of polychromatic light in a broad spectrum, and the pulses of light generated by the flashlamp illuminate the container and deactivate microorganisms within the container.
In a variation of this embodiment, the input port is specifically illuminated and microorganisms within the port are deactivated by the high-intensity, short-duration pulses of incoherent, polychromatic light in a broad spectrum.
In a still further embodiment, the invention can be characterized as an apparatus for sterilizing microorganisms in a drinking water container, wherein said container may include, for example, a polyolefin, such as polyethylene, and which transmits light in a spectrum containing wavelengths selected from between about 120 nm and about 2600 nm, e.g., wavelengths between 180 nm and 1500 nm or, e.g., between 180 nm and 300 nm. A flashlamp system generates high-intensity, short-duration pulses of polychromatic light in a broad spectrum, and the pulses of light generated by the flashlamp illuminate the drinking water container and deactivate microorganisms within the drinking water container.
In another embodiment, the invention may be characterized as an apparatus for deactivating microorganisms in a container which contains transmissive drinking water that transmits more than about one percent of light at a wavelength of 260 nm, and which container transmits light in a spectrum having wavelengths selected from between 120 nm and 2600 nm (see examples above). The embodiment also employs an input port coupled to the container through which the drinking water can be introduced into the container, and a flashlamp system that generates high-intensity, short-duration pulses of polychromatic light in a broad spectrum, and deactivates microorganisms within the container by illuminating the container with such pulses of light.
In an additional embodiment, the invention can be characterized as an apparatus for deactivating microorganisms in a container which includes a container having at least one input port through which the drinking water can be introduced into the container, and transmits light in a spectrum having wavelengths selected from between 120 nm and 2600 nm (see examples above); a flashlamp system that generates high-intensity, short-duration pulses of polychromatic light in a broad spectrum, and deactivates microorganisms within the container by illuminating the container with the pulses of light having been generated. The flashlamp of this embodiment advantageously deactivates sufficient microorganisms to achieve a sterility assurance level of at least 10xe2x88x926.
In an even further embodiment, the present invention can be characterized as an apparatus for sterilizing microorganisms at in a drinking water container. Such apparatus employs a flashlamp system including means for generating high-intensity, short-duration pulses of polychromatic light in a broad spectrum, and for deactivating microorganisms within the drinking water container by illuminating the drinking water container with the pulses of light having been generated; a photo-sensitive detector positioned so as to receive a portion of each of the pulses of light as a measure of an amount of light illuminating the drinking water container, for generating an output signal in response thereto; and a control system, coupled to the flashlamp system and the photo-sensitive detector, for determining, in response to the output signal, whether the pulses of light are sufficient to effect a prescribed level of deactivation of microorganisms in the drinking water container.
In still a further embodiment, the present invention can be characterized as a method for sterilizing microorganisms in a drinking water container, having steps of generating a high-intensity, short-duration pulse of polychromatic light in a broad spectrum; deactivating microorganisms at the drinking water container by directing the pulse of light having been generated at the drinking water container; receiving a portion of the pulse of light as a measure of an amount of the pulse of light illuminating the drinking water container; generating an output signal in response to the receiving of the portion of the pulse of light; and determining, in response to the generating of the output signal, whether the pulse of light is sufficient to effect a prescribed level of deactivation of microorganisms in the drinking water container. This embodiment includes a further embodiment wherein said output signal used to determine whether a prescribed level of deactivation of microorganisms in the drinking water container has been achieved, validates the sterilization process such that a sterility assurance level of at least about 10xe2x88x926 is achieved.
Further provided herein is a method of optimizing deactivation of microorganisms on and/or within a drinking water container, using high-intensity, short-duration pulses of polychromatic light in a broad spectrum, by automatically adjusting the intensity and/or duration of light exposure based upon parametric detection of the light. In particular, a photo-sensitive detector is employed to receive a portion of each pulse of light as a measure of the amount of light illuminating the drinking water container and that measurement is used to calculate the degree of deactivation of microorganisms occurring at the surface and/or within the drinking water container. In response to the measurements taken and calculations made, the intensity and/or duration of the pulsed light is adjusted to provide optimized deactivation. Further, these measurements can be, quite advantageously, used to validate sterilization of the drinking water container.